I sense a misperception of what MP Ratings is. MP Ratings is a glicko system and only deals with match play situation where someone plays someone else (either an individual or a group).
Single player games cannot be rated because you didn’t play someone else. In best game tournaments your result is ranked against other players, but you can’t say you “beat” another player. IFPA ratings makes that assumption and it’s why IFPA ratings are highly volatile and often useless.
In the case of a best game tournament followed by match play finals, MP Ratings doesn’t say that players who played match play outperformed players who didn’t. All it says is that Player A beat Player B and Player C beat Player D (and so on for every match played).
Players who didn’t play any match play games are omitted because they didn’t play any games that can be rated. I fail to see how that can make anything skewed – trying to infer results based on the best game portion would duplicate all the problems with IFPA ratings. I’m never going down that route – IFPA ratings already exist.
The consequence for players who didn’t make it to finals are miniscule. Their rating deviation goes up by a small amount (same amount it goes up every day they don’t compete). Their rating stays the same because they didn’t play any rated matches.
That said: Finding yourself at INDISC on Sunday with no finals to compete in would be an excellent time to play some Challenge Matches against people you don’t compete against very often! Those matches will all affect your rating and you get to play lots of fun competition pinball! https://matchplay.events/live/challenges